174 BOARD OF AGRICULTURE. 



ferent climatic conditions ; that in the north we have a sniall 

 amount of moisture falling in a fluid state upon the earth's sur- 

 face ; that we have to come to our latitude before we find a 

 climate which will produce alternately, at different seasons, rain 

 and snow, and we come finally to a climate further south where 

 no snow falls, but only water, we shall find that those climatic 

 conditions are so similar to those which now operate upon the 

 glaciers of the Alps, that we can have no doubt that to those 

 conditions alone may be ascribed the movement of the accumu- 

 lated snow of the north in a southerly direction, in the same 

 manner that we have now in the Alps a downward movement of 

 the snow into the lower valleys of the Alps in consequence of 

 the transformation of snow into ice. I have no doubt of this ; 

 and what confirms me in this opinion is the great thickness 

 which these masses must have had in former days. If we have 

 no great mountain chains from which these masses of ice can 

 have descended, we have at least mountain chains sufficiently 

 high to tell us to what level the action of ice has reached ; and 

 in the White Mountains I have found that up to the height of 

 five thousand feet the mountain slopes are polished, grooved and 

 scratched. In Maine I have not seen a hill the top of which is 

 not glacier worn. But notwithstanding these inequalities, the 

 mass of ice must have moved evenly southwards. Now, begin- 

 ning at Katahdiu and moving southwards towards the ocean, we 

 have a succession of hills which trend in a north-east south-west- 

 erly direction. On all these hills we observe the scratches and 

 grooves, as if these inequalities were no obstacles to the mass of 

 ice. That is, after passing one slope and coming down, they 

 ascend again and come down again, and rise again, until they 

 reach the seashore. Now a glacier does not move up and down 

 hills, but it moves evenly over inequalities. In the valley of the 

 Aar, for instance, we have several hills, the sides of which are 

 evenly polished and smooth, showing that the glacier, when it 

 was five thousand feet thick, moved over those inequalities, just 

 as a stream moves over the inequalities of its bed without being 

 stopped by those inequalities. But the stream would not flow 

 over them if it did not rise above them ; and so must this mass 

 of ice have been thick enough to move over these inequalities 

 without meeting an obstacle in the height of those hills. Some 

 of those hills arc fifteen or eighteen hundred feet high. I take 



